RMI Nuclear Justice Documents

Table 10

BRAVO Gamma or Beta Exponent

Indicated by Miller (0C68) for Fission Products
Time Post-Detonation,
t; to to

Decay Exponent,

(h)

m

1 to 2
2 to 3

-1.4
-1.2

48 to 96

-1.2

3
6
9
12
24

to
to
to
to
to

6
9
12
24
48

~.92
-.81
~.78
-.82
-1.0

CaCO3, 2.7-2.9. The granules were aggregates of smaller unit particles with
shapes that varied from spindles to cubes to spheres.
The size of these unit
particles making up the granules varied from 0.1 to 3.0 Um (4 x 1076 to 1.2 x
10°? in.). It was suggested by Suito that Bikini ash was formed by evaporation
of the coral reef to its constituent atoms and then by recrystallization of Ca

with Hj0 and CO9 in the air (Su56).

The granule size distribution of Bikini ash was used to estimate
the time over which the bulk of the activity fell on the fishing vessel. Most
of the activity was carried by larger-volume granules, which fell at early times
post-detonation (La65). The Bikini ash activity versus granule size distribution, % of total activity versus granule size, was plotted in Figure 4. To construct this histogram, we assumed the activity of a granule to be proportional
to the 3.5 power of its size. Lavrenchik summarized the results of many studies
and concluded that the activity of a granule was proportainal to the 3rd or 4th
power of granule size (La56). He generalized that the activity and volume of
the granule were proportional. The number of granules in each size class was re-

ported by Suito for Bikini Ash (Su56).

The size at median activity was 370 Um.

Our information regarding granule fall time as a function of granule size was derived from deposition models which were reviewed by Norment
(No66). Four models of fallout settling were presented. These models accounted
for granule size and initial height of the granule. Granule fall times from various heights were derived by Norment who used the model results of Davies,
Hedman, Hastings, or Ksanda. Although the complexity of each model varied, each
accounted for the aerodynamic properties of irregularly shaped fallout granules.
The granule fall time result versus granule size was recast by us using a power

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